Manufacture of aluminum hydroxide



Patented Feb. 24, 1925.

UNITED STATES 1,521,903 PATENT OFFICE.

GEORG MUTH, OF NUREMIBERG, GERMANY, ASSIGNOR TO THE AMBER STZE AND CHEMICAL COMPANY LIMITED, OF LONDON, ENGLAND.

No Drawing.

To all whom it may concem:

Be it known that I, Gnonc MUTH, a citizen of Germany, and residin at 20 Wetzendorferstrasse, Nuremberg,

ments in and Relating to the Manufacture of Aluminum Hydroxide, of which the following is a specification.

This invention relates of aluminum hydroxide.

It is known that natural double silicates or silico-aluminates such as potassium felspar (leucite), sodium felspar (albite, sodalithe, nephelin, &c.), may be decomposed by 16 treating them with caustic or carbonates of alkalies by wet processes under very high pressure.

In the double silicates in question there is a considerable proportion of impurities and 20 they contain such a large percenta of silica and have such a relatively sma content of alumina, for instance potassium felspar to themanufacture contains 75 per cent. of silica (SiO and onl 18 per cent of alumina (A1 0,), that 26 their treatment is not very remunerative from a commercial int of view. Not only is the cost of inding. such double silicates in order that t ey may be treated raised by.

reason of their content of im urities, but 30 apparatus for treating a doub e silicate or sillco-aluminate contalnin only 18 per cent of aluminum oxide must as large again as that which is necessary for treating simple aluminum silicates such as, for example, china clay whose content of aluminum oxide is roughly stated more than twice that of an equal wei ht of a double silicate. There is the further disadvantage that for convertin the naturaldouble silicate (which 0 is somew at resistant to the reagents used) into alkali-metal silicates, an extremely high ressure, namely 18 to 20 atmospheres, must e employed and this also has the elfect of.

Yrendermg the process costly.

The object of the present invention is to provide an improved process for the-maimfacture of aluminum ydroxide from natural aluminum silicates, such as china .clays. The present invention comprises heating '0 aluminum silicates with caustic alkalies or alkaline earths or alkali or alkaline-earth metal carbonates hereinafter referred to as alkaline bodies in the presence of water in a closed vessel at temperatures sufiicient to ermany, have in- 6 vented certain new and useful Improve MANUFACTURE OF ALUMINUM HYDROXIDE.

Application filed November 24, 1924. Serial- Ho. '752,006.

give rise to a pressure of 3 to 4 atmospheres, 5 or .in the absence of water to like tempera, tures, namely to a temperature of. 134 to 144 C.

The invention also comprises heating, aluminum silicates, such as china clays, with alkalies or alkaline-earths or their carbonates in the presence of water to the boiling temperature to obtain easily decomposable alkali or alkaline-earth-metal aluminum silicates, and heating the resulting double silicates with a further proportion of alkali in a closed vessel in the presence of water to a temperature sufiicient to give rise to a pressure of 3 to 4 atmospheres, or in the absence of water to like temperatures to efl'ect its decomposition, namely to a temperature of 134 to 144 C.

The following particulars are given by way of example to illustrate suitable methods of carrying the invention into effect;-

gether in proportions yielding a mixture containing 1.2 to 1.5 molecules Na O to each molecule A1 0 for example in the case of china clay containing 40 per cent of A1 0,, for each parts of clay a pro ortion of caustic soda equivalent to 30 to 3 parts of Na,O is added, whereupon the mass is boiled for some time at atmospheric pressure and finally under a pressure of 3 to 4 atmosheres. The resulting alkali-metal silicate IS SB arated from the aluminum hydroxide whic may be treated by known processes to form aluminates, alummum salts or metallic aluminum.

Example II.

Double silicates or silico-aluminates are produced by heating a mixture of china clay and caustic soda to a temperature of about 100 C. For instance, in the case of a clay containing 40 per cent of aluminaa proportion of caustic soda equivalent to 15 to 18.5 100 parts of Na,O is added to each 100 parts of clay; After heating to 100 C. the roduct is mixed with a further proportion o caustic soda equivalent to 15 to 18.5 parts by wei t of Na O to each 100- parts of clay. he whole is then heated in the dry state to a temperature such as. would give rise to a pressure of 3 to 4 atmospheres if a similar mixture containing water were heated in a closed vessel. On treating the product with water, sodium silicate may be extracted, leaving aluminum hydroxide as a residue; As will be understood, if desired, the whole of the alkali necessary to secure the decomposition of the china clay may be added at once and the dry mixture heated to a temperature such as would give rise to a pressure of 3to 4 atmospheres if a similar mixture containing water were heated in a closed vessel.

It will be appreciated that in so far as the present invention is concerned with the employment of alkaline earth metal compounds in o ening up aluminum silicates, it is clearalumina from the aqueous extract.

istinguished from processes involving Having now described my invention what I claim as new and desire to secure by Let ters Patent is Process for the manufacture of aluminum hydroxide and water-soluble silicates from natural aluminum silicates, which comprises heating aluminum silicates with alkaline bodies in the presence of water to the boiling temperature at normal atmospheric pressure to obtain an easily decomposable double silicate and heating the resultant double silicate with a further proportion of alkali to a temperature in the neighbourhood of 140 C. a

In testimony whereof I have signed my name to this specification.

: GEORG MUTH. Witnesses ADE Do'rm, ALExIs v. PHImProFL. 

